1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus such as a copying machine and a printer, and more in particular to the electrophotographic image forming apparatus which reduces an area for installing the apparatus.
2. Description of the Prior Art
An image forming apparatus such as a printer is generally connected as a peripheral equipment to a superior device, such as computer. When an operator activates printing operation from the superior device, a predetermined printing output is obtained from the image forming apparatus. Considering the operation efficiency, it is most desirable that the superior device and the image forming apparatus are disposed at an identical place. Particularly, in the apparatus to be connected with a desktop type superior device such as a personal computer or an engineering work station, the best arrangement is such one as the superior device and the image forming apparatus are disposed on one identical desk, and thereby an operator's working space is ensured. Recently, ink jet type printers has been reduced in the size as capable of providing the foregoing circumstance is available. However, a further size reduction is necessary for the electrophotographic type apparatus. To reduce the size, various improved inventions have been made. Such examples of the prior art image forming apparatus are to be explained with reference to FIG. 1 to FIG. 3.
In FIG. 1, a photoconductor drum 51 is provided on a paper feeding path 50 which is disposed in parallel with a bottom of the printing apparatus of FIG. 1, and a developing device 54 and other image forming devices 52 and 53 are disposed at the periphery thereof. The developing device 54 produces toner images on the surface of the photoconductor drum 51. A transfer device 55 for transferring toner images to a sheet of paper is disposed by way of a paper transportation path just beneath the photoconductor drum 51. The sheet of paper sent from a paper cassette (not shown) is transferred with the toner images of the photoconductor drum 51 by the transfer device 55 and then fixed with the toner images by a fixing device 58 disposed near the downstream end of the paper feeding path 50 and then discharged. A cleaning device 56 removes the remaining toner on the photoconductor drum 51.
Such a constitution has a laterally elongate constitution by restricting the height to some extent.
Further, another image forming apparatus as shown in FIG. 2 has also been used at present. In FIG. 2, a cleaning device 62 including cleaning roller 63 and a developing device 65 are disposed so as to vertically put a photoconductor drum 61 therebetween and a paper transportation path is disposed so as to surround a lateral portion of them vertically for one-half circumference. A transfer section 66 is disposed corresponding to the photoconductor drum 61 on the side of the paper transportation path, and an exposure section 64 is provided on the opposite side by way of the photoconductor drum 61. The sheet of paper is fed by a paper cassette 68 disposed in parallel with an installing plane and discharged along the paper transportation path to a fixing device 67.
With a such a constitution, the lateral width of the apparatus is reduced compared with the prior art example shown in FIG. 1 because the paper cassette 68 is positioned beneath the printing device.
On the other hand, Japanese Patent laid-open Hei 5-301398 discloses another image forming apparatus as shown in FIG. 3. The image forming apparatus has a paper transportation path 71 substantially in parallel with an installing plane 78, a photoconductor drum 74 disposed at a central portion of the apparatus along the paper transportation path 71, and developing device 77 and other image forming devices disposed so as to surround the photoconductor drum 74. A paper feed cassette 72 and a paper discharge tray 73 are stood vertically in the upper portion of the apparatus. Among them, the paper feed cassette 72 is provided above the upstream end of the paper transportation path 71 being inclined outwardly, and a pick roller 70 is disposed between the paper delivery side thereof and the developing device 77. This is intended for the size reduction.
In addition to them, as shown, for example, in Japanese Patent Laid-Open Hei 4-310968, there is also such an image forming apparatus that an electric equipment portion for controlling the image forming operation, a paper transportation path and a developing section are located successively above a paper cassette loaded in parallel with the installing plane thereby reducing the size of the apparatus.
However, each of the foregoing examples of the prior art involves the following disadvantages.
In the image forming apparatus shown in FIG. 1, since the paper transportation path 50 is disposed in parallel with the installing plane, and the paper cassette is loaded in parallel with the installing plane at the upstream end thereof, it requires a lateral width at least about twice the paper length and has a disadvantage of requiring a large installation area.
In the image forming apparatus shown in FIG. 2, since the paper cassette 68 is loaded in parallel with the installing plane, it is impossible to shorten the width of the apparatus depending on the length of the paper cassette 68. Therefore, it suffers from a disadvantage that the installing area can not physically be reduced.
In the image forming apparatus shown in FIG. 3, the paper feed cassette 72 is stood vertically being inclined outwardly, and the pick roller 70 has to be disposed between the paper feeding side of the paper feed cassette 72 and the developing device 77. Therefore, it is difficult to shorten the paper transportation path between the paper feed cassette 72 and the developing device 77. Accordingly, although the feed cassette 72 is installed above the apparatus, there is a drawback that the effective installing area can not actually be diminished.
Further, also the image forming apparatus as disclosed in Japanese Patent Laid-Open Hei 4-310968, since the paper cassette is loaded in parallel with the installing plane like that illustrated in FIG. 2, it is impossible to shorten the width of the apparatus than the length of the paper cassette on the installing plane and it involved a disadvantage that the installing area could not be reduced to more than a predetermined extent from a physical point of view.